For decades, Taiwan has maintained a strict policy of refusing to allow any letters or telephone calls between its citizens and the Chinese mainland.

Taiwan government spokesmen said this prohibition was one aspect of its policy called the "three nos": no negotiations, no compromise and no contact with China under its Communist leadership.

But in an era of advanced communications technology, Taiwan's policy has become increasingly difficult to enforce, at least with respect to phone calls. China's 1 billion citizens now enjoy apparently wide latitude to call up relatives and friends among Taiwan's population of 19 million.

This week, a Times reporter inquiring about the state of relations between China and Taiwan had no difficulty in placing three separate calls from Peking to Taipei--including one call to Taiwan's Government Information Office, the agency which speaks for the Taiwan government.

Clear Connection

"I don't think phone calls from the mainland to here are permissible," said Charles Chen, a Taiwan government spokesman, during an eight-minute conversation over a clear phone line on Thursday. "Sometimes calls do get through, but that doesn't mean we allow the calls to happen."

Chen expressed surprise when informed that he was speaking with someone phoning from Peking.

"I really shouldn't be talking to you then," he said. "Would you just forget all I said to you?"

Earlier in the week, Taiwan had loosened up on another part of its "three nos" policy when it agreed for the first time to permit direct, face-to-face negotiations between officials of its national airlines and their counterparts from China.

Hong Kong Meeting

Aviation officials from the two countries are preparing to meet in Hong Kong to discuss the fate of a Boeing 747 cargo plane from Taiwan's China Airlines and two of its crew members. The pilot landed the aircraft in the Chinese city of Canton on May 3 and announced that he wanted to live with his family on the mainland.

On Thursday, the two sides announced that the talks will begin today. The phone calls Thursday were not the first ones ever to be placed from China to Taiwan.

In 1979, Peking-based reporters for the Agence France-Presse and Reuters news agencies managed to place calls from Peking to their Taipei offices or to hotels in Taipei. Late last year, there were reports of international direct-dial calls being made from South China's Fujian and Guangdong provinces to Taipei.

First Such Call

No cases have previously been reported, however, of phone calls put through from China to government agencies or spokesmen in Taiwan. A foreign analyst in Taiwan contacted from Peking on Thursday also said it was the first such call he had ever received and the first one of which he had ever heard.

The calls were placed through a Peking operator, who expressed no surprise at the request for a Taipei phone number. Each of the the calls was put through within 15 minutes.

The operator explained that she was placing the calls by using an international direct-dial number. She declined to respond to inquiries about whether the calls were being routed through Hong Kong.

In the past, Taiwan officials have said that phone calls from China to Taiwan are simply not possible because there is no service agreement or contract between the two countries. Furthermore, Taiwan's agreements with other jurisdictions such as Hong Kong and Japan specifically forbid calls to be put through to the island from the Chinese mainland.